Process for the removal of foreign particles from gases



Patented a. so. 1940 a. 7 2,188,439 Q UNITED" STATES PATENT- omen PROCESS FOR THE REMIOVAL OF FOREIGN PARTICLES FROM, GASES George M. Kirkpatrick, Pittsburgh, Pa., assignortoBlaw-Knox Company, Pittsburgh, Pa., a corporation of New Jersey No Application lune so, 1938', Serial No. 218.847

c Claims. ((21.252-1) This invention relates to an improved process tions-to obtain a low viscosity, of the order offor the removal of foreign particles from gas. 30 to 60 seconds Saybolt at 100 F. The follow- Gas used for industrial purposes, for example, ing examples are illustrative of my invention. natural or artificial fuel gas, often contains solid Example 1.-A commercial mineral lubricating 5; matter in the form of dust, flne droplets or oil and dibutyl phthalate were mixedin the pro- 5 spray, which it is desirable to remove at some portion of 80% of oil to 20%'of dibutyl phthalate. point or another in the distribution system, The oil had a viscosity of 240 seconds Saybolt This removal maybe accomplished largely or at 130 F. This viscosity did not increase exentirely by contacting" the gas with a liquid, cessively as the temperature was lowered. The

3Q which liquid serves to entrain or dissolve the oil had a flash point of,600 F. The dibutyl solid matter in the gas. Various contacting dephthalate had a viscosity of 8 seconds Saybolt vices are in use. The most eflective of them at 100 F., a flash point of 168 C., a volatility achieve an intimate contact between the liquid of 3.74% in six hours at 100 C., and a vapor and the gas by forming the liquid into a spray .pressure of .25 mm. of mercury at 180 C.

I! or rain through which the gas passes. Such a The oil and the dibutyl'phthalate-are miscible lli contactor is shown in Sillers Patent 2,048,145, in all proportions from-zero to about 30% of dated July 21, 1936 dibutyl phthalate by volume. The addition of The contacting liquid heretofore employed has the dibutyl phthalate lowers the viscosity of the enerally been a mineral oil, although other liqmix. The proportions may be varied under difuids have been proposed. The liquids heretofore ferent circumstances, but the percentage stated used have not been entirely satisfactory, either has been found to give an excellent mixture because of the absence of desired physical propwhich functions satisfactory and is not unduly erties, or because ofexpense. A notable shortcostly. The mixture has a viscosity between coming of contactor fluids heretofore employed and 50 seconds Saybolt at 100 F. It does not #5 is so-called c'arry-over'g'. By this is meant the volatilize nor fog in a Sillers contactor at or- 25 inclusion inthe' stream of gas as it issues from dinary atmospheric temperatures, and may be the contacting apparatus of a portion of the readily reduced to the form of a spray or rain. contact liquid either because it has been vola-- It is not necessary to use. purified dibutyl tilized or because it has been reduced to a fine phthalate as it is ordinarily supplied to the marmist or fog which cannot be recovered in apket. The final purifying steps usually taken may 80 paratus of economical size. The carry-over be omitted, resulting in a materially lower cost. naturally results in a depletion of the normal Example 2.--The contacting liquid used in Exsupply of liquid available for cleaning purposes. ample 1 may be improved by the addition of a I this requiring continuous or frequent supply of wetting agent" such as octyl alcohol. vThe funcadditional cleaning liquid. This is most unsatistion of the wetting agent is to enable solid par- 35 factory because in many cases it is desirable that ticles entrained in the gas to more. readily penethe periods between replenishments of liquid in a trate the surface film of the droplets. The vapor contactor be very long, sometimes an entire year. pressure of octyl alcohol is .28 mm. at 20 C.

It is also unsatisfactory because the liquid. used From ,5 to 1% of this wetting agent, when added '40 is relatively expensive and its depletion adds to to the fluid of Example 1, materially improved 40 the final cost of the gas supply. Other disadvanthe capacity of the fluid to remove solid particles tages of carry-over are that the fog ultimately from suspensionin fuel gases and did not apcondenses into liquid or viscous matterin the pipe preciably otherwise afiect the physical properties lines and fixtures beyond the contact apparatus, of the fluid.

$8 and also, in certain cases, may have an injurious Example 3.Castor oil in the proportion of efiect upon the use to which the gas may be put. 60% or less was mixed with dibutyl phthalate in Ihave discovered that these shortcomings may the proportion of 40% or more. The lower be cured. and a contact liquid of superior charquantity of dibutyl phthalate was preferred beacter and performance may be obtained, by using cause of cost. The castor oil was highly viscous '00 a mixture of liquids so as to produce a compound and non-volatile, having a flash point of 235 C.

fluid having certain physical properties. I emand an ignition point of 423.4 C. play at least two liquids, each of which is relative- It will be noted from the above examples that ly non-volatile at ordinary temperatures. Howvarious oils may be employed.- with mineral ever, the liquids employed have widdy' diflering oils dibutyl phthalate may be successfully used in II viscosity and they are mixed in suitable propcrthe amount of 10 to 30%. If the oil is rdativ'ely non-viscous or what is known as a "light oil,

the amount of dibutyl phthalate employed may be reduced. The octyl alcohol referred to in Example 2 gives useful results in the range of from A to 1%.

In place of dibutyl phthalate, other liquids commonly described as esters or as plasticisers, because of uses to which they are sometimes put, may be substituted. Among these may be mentioned tricresylphosphate, triacetin, diamyl phthalate, diethyl phthalate, dibutyltartrate, triphenyl phosphate, octyl acetate, Carbitol acetate. Carbitol acetate is a trade name for diethylene glycol mono-ethyl ether acetate. These are variously misicible with mineral lubricating oils, some forming emulsions instead of true solutions, and some requiring catalysers to produce miscibility. As the present time, however, because of price, dibutyl phthalate is preferred. This particular liquid, moreover, has the advantage of readily absorbing tar and asphalt which is an advantage in treating certain fuel gases.

My improved process has many advantages. The fluid is not volatile in any substantial degree over the temperature range required, which will generally be from some degrees below zero to about 130 F. It is readily reducible to a spray composed of small drops, but it does not become so finely divided as to produce a fog or a mist. It retains this property-over the required temperature range. Its surface tension is low and particles suspended in the gas undergoing treatment readily penetrate the surface of the droplets with which they come in contact and are thereby transferred from suspension in the'gas to inclusion in the liquid. As stated, this property may be enhanced by the addition of a wetting agent. The liquid does not react chemically with the gas under treatment.

In certain instances it may be desired to add a constituent to thegas and this can be done by mixing such constituent with my improved liquid. Needless to say, if such procedure is followed there will be a depletion of the liquid or at least of the constituent which it is desired to add to the gas.

While I have described certain preferred embodiments of the invention, it will be understood that these are by way of example only and that the invention may be otherwise practiced or embodiedaglithin the scope of the following claims.

I cl

1. A process for the removal of foreign particles from gases which comprises bringing the particle laden gas to be treated into intimate contact at temperatures within the normal atmospheric range with a fluid consisting essen- 8 tially of a mixture of two liquids, each relatively non-volatile at ordinary temperatures but of different viscosity, the mixture being substantially non-volatile below 130 Rand having a viscosity of the order of to seconds Saybolt at F. 10

2. A process for the removal of foreign particles from gases which comprises bringing the particle laden gas to be treated into intimate contact at temperatures within the normal atmospheric range with a fluid consisting essenl0 tially of a mixture of an ofl and a viscosity modifler of the group dibutyl phthalate, diamyl phthalate, diethyl phthalate, dibutyltartrate, triphenyl phosphate, octyl acetate, CarbitoP' acetate, the mixture being substantially non-volatile below 211 F. and having-a viscosity of the order of -30 to 60 seconds Saybolt at 100..F.

3. A fluid for the removal of foreign particles from gases consisting essentially of a mixture of oil and dibutyl phthalate, the mixture being sub- 8! stantially non-volatile below 130 F. and having a viscosity of the order of 30 to 60 seconds Saybolt at 100 F. a

' 4. A fluid for the removal of foreign particles from gases consisting essentially of a mixture of II! a, mineral oil and dibutyl phthalate, the dibutyl phthalate being present in the amount of approximately 20%, the mixture being substantially non-volatile below 130 F. and having a viscosity of the order of 30 to 60 seconds Saybolt at 100 F.

5. A fluid for the removal of foreign particles from gases consisting essentially -of a mixture of two liquids, each relatively non-volatile at ordinary temperatures but of different viscosity, the mixture being substantially non-vola- 4t tile below 130 F. and having a viscosity of the order or 30 to 60 seconds Saybolt at 100 F., and a wetting agent.

6. A fluid for the removal of foreign particles from gases consisting essentially of a mix- 4 ture of two liquids, each relatively non-volatile at ordinary temperatures but of different viscosity, the mixture being substantially non-volatile below 130 F. and having a viscosity of the order of 30 to 60 seconds Saybolt at 100 F., and 5 octyl alcohol.

' GEORGE M. KIRKPATRICK. 

